At-home core strengthening without weights?
I'd like to get my upper body into slightly better shape- especially because I can really feel my back begining to hurt after an hour on the saddle.
What kind of exercises would you recommend for at-home core strengthening? I'd like to avoid weight lifting because I'm 16, and also because I'd rather not purchase additional fitness equipment.
Yoga? Pilates? I'm open to all suggestions.